Synchronous communication system



Jan. 4, 1938. H. J. NICHOLS ET AL 2,104,572

SYNCHRONOUS COMMUNICATION SYSTEM Filed g- 1934 5 Sheets-Sheet 1 IN VENTOR W WM J Jan. 4, 1938. H. J. NICHOLS ET AL SYNCHEoNOUS COMMUNICATION SYSTEM Filed Aug. 7, 1934 5 $heets-Sheet 2 5 an" .n h e/ 2M 1M1 M w 2 II OJ cd g B/mF a a/w 1 m S 2 INVENTOR A TTO Jan. 4, 1938. J MCHOLS ET AL 2,104,572

SYNCHRONOUS COMMUNICATION SYSTEM Filed Aug. 7, 1934 5 Sheets-Sheet 5 SOURCE DIRECT C u RRENT 8.6. POWER Fig. 5.

A TTORNE Y5 Patented Jan. 4, 1938 UNITED STATES PATENT OFFICE SYNCHRONOUS COMMUNICATION SYSTEM York Application August 7, 1934, Serial No. 738,833

Claims.

This invention relates to a synchronous communication system and more particularly to single impulse printing telegraph systems.

A general object of the invention is to provide an improved system for printing telegraphs whereby the speed and accuracy of transmission can be improved.

Another object of 'the invention is to provide a transmission system for printing telegraph of the single impulse type whereby the printing signals are distinguished by character as well as by time.

A further object of the invention is to provide a transmission system whereby signals which are the same in respect to time are distinguishable because of being of opposite polarity.

A further object of the invention is to provide a transmission system of the synchronous, single impulse type employing unidirectional periodic synchronizing signals and bidirectional aperiodic printing signals.

A further object is to-provide a method and apparatus for utilizing periodic synchronizing signals for call signalling purposes as well as for synchronizing purposes.

Other objects and features will be in part obvious and in part hereinafter pointed out in connection with the following description, the accompanying drawings, and the appended claims.

Synchronous single impulse printing telegraph systems as contrasted with coded signal systems, depend in the matter of selection upon dividing time into units, represented usually by a single revolution of a rotating member, and subdividing such units into fractions equal in number to the selections to be performed. The signals representing desired selections are thus difierentiated from each other by the times at which they are caused to appear as measured from zero timethe commencement of each revolution of the rotating member.

In the novel system herein disclosed, each fractional time unit may represent a plurality of desired selections, the signals for each of the plurality of selections being distinguished in respect to character such as polarity, frequency and/or amplitude. For example, the basic time unit may be sub-divided into fractions equal in number to one-half the number of selections to be performed and the two signals associated with each fractional time unit may be distinguished by polarity. The basic advantage in transmission thus gained may be utilized to double the speed of transmission or to double the number of selections without decreasing the duration of the signals representing the fractional time units; to double the length of the signals; to increase the synchronizing margin; or to obtain a combination of these benefits in part. If a rotary distributor is employed, the distributor may have approximately one-half the normal circumference; if a type wheel is employed, together with suitable printing arrangements, the circumference of the typewheel may have approximately one half the normal number of printing arcs.

In the drawings, Fig. 1 shows a diagram illustrating the advantages of the signalling system of the invention compared to single impulse signailing systems heretofore used.

Fig, 2 shows in diagrammatic form circuits and apparatus illustrating the invention applied to the sending end of a typical printing telegraph system.

Fig. 3 shows in a similar manner one embodiment of the invention as applied to the receiving end of a typical system;

Fig. t shows another embodiment, utilizing electronic relays, as applied to the receiving end of the system;

Fig. 5 shows in diagrammatic form a simplified arrangement for both sending and receiving as applied to a complete printing telegraph unit;

Fig. 6 shows a side view in part section of a phase corrector mechanism constituting a preferred form of apparatus to be used in connection with the invention.

Fig. 7 shows a plan view in section of the phase corrector mechanism of Fig. 6 the section being taken along line of Fig. 6.

In the several figures, excepting Fig. 1, like characters represent like parts.

Referring to Fig. l in detail, line A illustrates graphically the signals of a single impulse printing telegraph system employing continuous periodic synchronizing signals and aperiodic printing signals, S representing the synchronizing signals and P the printing signals. The time interval between the beginning of two successive synchronizing signals, representing one revolution or cycle of the distributor, is the basic time unit and is designated by the letter T. The speed of transmission is directly related to this interval. If there are N selections plus synchronizing to be performed over the system, the signal impulses are represented by a fractional time unit equal to T divided by N +1, which fractional time unit is designated on the diagram by t, and theoretically printing signal. In practice, some synchronizing shorter.

Line B illustrates graphically the signals in accordance with the present invention. It is assumed that the distributor speed is the same as in the previous case, hence the time of one revolution is likewise represented by T. Assuming again that there are N selections plus synchronizing to be performed, the fractional time unit representing the duration of the signals is equal to T divided by N/2+1, since both positive or negative signals are used for printing selections. Since N in practical systems is 30 or greater, the fractional time units in the system of the invention are approximately equal to 2t, and are so designated in the diagram.

Fig. 1 represents conditions when the advantage of the invention is utilized in lengthening the signals without increasing the speed of transmission. As previously mentioned, other advantages are to be gained, including that of practically doubling the speed of transmission without decreasing the length of the signals. For example, let it be assumed that the series of printing segments on a particular rotary distributor are combined in pairs, and are re-arranged into two series of one-half the initial length, while the linear velocity of the distributor is kept the same. Therefore, on the average, only one-half the normal time interval elapses before the distributor arrives at the segment associated with any selected character, and the speed of transmission is therefore doubled.

Referring toFig. 2 in detail, the apparatus shown performs the function of transmitting periodic synchronizing and aperiodic printing signals to the line. Local current impulses, which produce the line signals, are collected from their respective circuits by a rotary distributor comprising a rotary contactor 20 sweeping at uniform speed over the face of common ring 2| and a series of insulated segments lettered S, a, b, c, d, etc. mounted in radial pairs in two circles concentric with ring 2| and the axis of rotary contactor 20. These parts are illustrated in linear development to simplify the diagram.

Two printer actuating key levers 22a and 22b are shown, these key levers each representing a series comprising approximately one-half the actuating levers of the printer key board. Key lever 22a represents the series of key letters adapted to send printing signals of one character, say of positive polarity, while key lever 22b represents those sending printing signals of different character, say of negative polarity. Each key lever is shown with an individual key switch 23 operated by a push rod 24. The key switches are connected to one of a pair of sending busses, designated by 25a and 25b respectively. These busses are connected to the terminals of a centertapped resistor 26, which terminals are also connected to line terminals 21a and 21b. Battery B, or other source of direct current, provides current for signalling purposes. One side of battery B is connected to ring 2i, and the other side to the center tap of resistor 26.

The operation is as follows: Assuming that rotary contactor 20 is in rotation, when it reaches segment S, called the synchronizing or unison segment, a circuit is completed from positive buttery to ring 2|, via contactor 20 to segment S, via send bus 25a through section 26a of resistor 26 to center tap and thence to negative battery. A current pulse flows through the circuit just traced for the duration of contact of contactor margin is required, and the signals are somewhat- 20 with segment S, causing a corresponding potential pulse to appear across section 26a. The line terminates in some item of receiving equipment such as a relay, transformer, or vacuum tube which completes the line circuit, hence part of the current pulse flows through the line circuit, returning to the center-tap via section 26b. The line potential pulses, or current pulses caused thereby, constitute the line signals. The periodic signals sent each time contactor 20 contacts segment S constitute the synchronizing signals.

Assuming next that with contactor 20 still in rotation, key 22a is depressed, when contactor 20 contacts segment a, a circuit is completed from positive battery to ring 2! via contactor 20 to segment a, via key switch 23a and send bus 25a, through resistor section 26a and center tap connection to negative battery. The current pulse flowing through the circuit just traced produces a corresponding line signal as described in connection with the sending of the synchronizing signals.

It may be assumed that all signals sent via send bus 25a are positive signals.

Assuming next that key 22b is depressed, when contactor 20 arrives at segment I), a circuit will be completed from positive battery to ring 21 via contactor 20 to segment b, via key switch 231) and send bus 25b through resistor section 26b in the reverse direction, causing a negative signal to be sent to the line; hence all signals sent via send bus 251: are negative signals.

The aperiodic signals transmitted when the printer keys are depressed constitute the printing signals, and it is to be noted that signals which are similar in respect to their time relation to the synchronizing signal are distinguished by their polarity. Keys 22a. and 22b of course represent distinct characters to be printed, and are likewise representative in action of other pairs of keys associated with other segments.

It will be apparent to those skilled in the art that various well known arrangements may, following the method herein disclosed, be used to cause the reversal of polarity of the line signals, or other changes in their character, and all such variations should be and are intended to be encompassed in the terms of the appended claims.

Referring now to Fig. 3 in detail, keys 22a and 22b of the receiving apparatus correspond to those similarly designated at the sending apparatus in Fig. 2, and are actuated by key magnets [22a and l22b respectively, connected to segments a and b on one side, and to receive-busses 29a and 2% respectively on the other side. It will be understood that all key magnets for the series of key levers sending positive printing signals are connected to receive bus 29a, while those for the series of key levers sending negative printing signals are connected to receive bus 29b.

A suitable receiving instrument, such as polar relay 30, with tongue set to neutral, is so connected to the line that a positive signal impulse will cause the relay tongue to move to P, the upper contact, while a negative signal will cause the tongue to move to N, the lower contact.

The operation is as follows: Assume that a positive signal has been sent from segment a of the sending machine. Rotary contactor 20 is considered to be in synchronism with the rotary contactor of the sending machine, and is therefore in contact with segments a and b. The positive signal moves the tongue of relay 30 to contact P completing a circuit from negative battery via tongue and contact P to receive bus 29a, through winding of key magnet l22a to segment a, via contactor fill to ring 2i and return to positive battery. A local current pulse through this circuit energizes ,key magnet I22a, whose armature is operated, pulling down key lever 22a and actuating the printer mechanism to print the desired character.

It is readily seen that when a negative signal is sent to the line by key 22b at the sending machine, the movement of the tongue of relay 30 to contact N connects receiver bus 291) to nega tive battery, and contactor 20 completes the circuit of key magnet i221; through segment I), causing key 22b of the receiving machine to be actuated.

Referring to Fig. 4 in detail, polar relay 3!] of Fig. 3 is replaced in function by two electronic relays 40a and Mb. Each electronic relay, preferably of the grid controlled, gaseous discharge type, is provided with a control grid 4i, an anode 42, and cathode 43. The signals from the line are applied to the grids of relays 40a and 402)- by input transformer 44 provided with primary 45 and center-tapped secondary 46. The anode current for each relay is supplied by battery B, and the grids are given a normal bias by battery B connected to the center tap of secondary 46, and thence through windings 46a and 46b to the grids of relays 40a and 4% respectively.

As is well known, the grid of a gaseous discharge tube can start the ionization of the tube, but is normally unable to stop the discharge through the tube when once started. A cut-oil relay M is therefore provided to cut ofi the current in the anode-cathode circuits of the electronic tubes, one cut-off relay serving for both tubes.

The operation is as follows: When a positive signal is received from the line, the grid of relay 40a is rendered more positive than normal, and the grid of relay 4% is rendered more'negative than normal. Assuming the signal to be of suitable amplitude, relay 40a is ionized, while relay lllb is guarded against ionization. Assume that the signal was sent from segment a of the sending machine and that contactor 20, being properly synchronized with the rotary contactor of the sending machine, is likewise on segment a as shown. A circuit is then completed from negative battery through the winding of cut-off relay ll, via contacts of relay 4'! to cathode 43a of tube Alla, thence via electronic current to anode 42a, thence to receive bus 29a and through the winding of key magnet H211 to segment a, thence via contactor 20 and ring 20 to positive battery.

A current pulse flows through this circuit, energizing key magnet i22a which pulls down key lever 22a, printing the desired character. After a predetermined time interval, relay 41 opens its contacts, cutting off the current pulse, and permitting tube 400. to de-ionize.

It willbe apparent without further analysis, that when a negative signal is received with contactor 20 on segment b, relay 40b is ionized and key lever 22b will be actuated and the desired character printed.

Referring to Fig. 5 which illustrates the application of the invention to a complete printing telegraph unit, a combined arrangement for both sending and receiving, together with synchronizing means, is shown.

A three-position send-receive switch is preferably used to switch the circuits from neutral or typing position to sending or receiving, and the contacts operated by this switch are shown in convenient locations in the diagram and are numbered from i to H inclusive, the direction of operation to establish sending and receiving conditions being indicated by S and B respectively.

Two groups of key levers are shown, one group associated with positive signals, the other with negative signals, these groups being shown on either side of common ring 2! in order to facilitate the tracing of circuits. The circuits areshown in neutral condition, ready to receive a call signal. Direct current is shown as being supplied from a suitable source such as a rectifier, and is applied to the terminals of a voltage divider, the arrangement being equivalent to the batteries shown in previous figures.

The arrangement includes call-signalling means such as a bell 48 or other signalling device which may be actuated to call the attention of an operator at the receiving machine.

To start sending synchronizing signals, the send-receive switch is moved to send position, opening contacts 2-3, and closing contacts I--2, 9-40, and l-ll. Closing contacts 1- energizes magnet RM which withdraws armature 28 from the path of rotary contactor 20 which latter is put into rotation by its friction drive. Thereafter, on each revolution, magnet RM is re-energized, and hence remains operated and does not interfere with the rotation of contactor 20. Assuming rotary contactor 20 to be in rotation, on its arrival at segment S, a circuit is completed from positive battery to ring 2!, via contactor 20 to segment S, via contacts III-9 through send bus 25a and resistor section 26a to ground, thence returning to negative battery. A local current pulse through this circuit during the passage of rotary contactor 20 across segment S sends a synchronizing signal to the line via contacts l-2, as described in connection with Fig. 2. The printing signal sending arrangement is identical with that shown in Fig. 2, and its operation is readily apparent. Likewise, the manner in which the printing signals are received is similar to that shown in Fig. 3.

Assuming now that Fig. 5 represents the receiving machine, and that the send-receive switch is in the neutral position as shown, the manner in which the synchronizing signals are utilized to actuate a calling device, such as bell 48, is as follows: The received synchronizing signals traverse a circuit from one line terminal, say terminal 21a, via contacts 2--3, 5-4 to one terminal of hell 48 thence through its windings to the other bell terminal, and thence returning to line terminal 21b. The synchronizing signals thus energize and actuate bell 48, producing a call signal. When the send-receive switch is moved out of the neutral position, contacts 2-3, or else 5-4 are opened, and the line circuit switched to the sending or receiving device, as the case may be, hence the bell is switched out of the line circuit on sending or receiving. If an acknowledgment or call-back signal is desired, the preferred procedure is for the calling operator to throw the send-receive switch of the sending ma chine to send position in order to transmit calling signals for an interval, and then return the sendreceive switch to neutral position for an interval, during which latter interval the called operator may signal acknowledgment by throwing the send-receive switch of the receiving machine to send position.

,In case the line signals are not of sufiicient strength to operate a bell or other calling device directly, it will be obvious that a sensitive relay controlling a calling device energized from a local power supply may be employed, the relay replacing the bell in the example shown.

It will be further apparent to those skilled in the art that various well known devices and arrangements may, following the methods herein disclosed,'be used for producing an audible or visual call signal, and all such variations for employing the synchronizing signals of the invention' for call signalling purposes should be and are intended to be encompassed in the terms of the appended claims.

Referring again to Fig. 5, with the send-receive switch thrown to the receive position the synchronizing signals are received and utilized for purposes of synchronization as follows: The synchronizing signals actuate line relay 30, of quick-acting, quick-release type, contacts P being closed during the reception of each synchronizing signal. It is to be assumed that rotary contactor 28 is frictionally driven, but is held at rest on segment S by armature 28 of release magnet RM whose winding is included in the circuit connected to segment S. Release magnet RM is of quick-action, slow-release, pulse sustained type, adapted to release rotary contactor 20 when energized. For illustrative purposes, armature 28 of RM is shown in engagement with contactor 20.

On either side of segment S are located corrector segments, designated by SI and S2, having corrector magnets MI and M2 connected in series therewith as shown.

The operation of the apparatus just described is as follows: When the first synchronizing signal is received, relay 30 closes contacts P producing a local current pulse from negative battery via contacts P, receive bus 29a via contacts 8l, through winding of RM, to segment S, via contactor 20 to ring 2I thence to positive battery. Magnet RM is thus energized, releasing contactor 20 which is quickly put in rotation by its friction drive. Owing to a slight delay instarting, contactor 20 may lag slightly and at the instant when the second synchronizing signal is received may be in contact with segment Si, passing on to segment S during the latter part of the local current pulse. In such case, Ml is energized, causing contactor 20 to be advanced in phase by corrector means CM presently to be described. RM is also reenergized and sustained by-the second synchronizing signal, hence remains operated and does not interfere with the rotation of contactor 20. On successive synchronizing signals, contactor 20 is advanced in phase by the phase corrector until the entire synchronizing signal is received on segment S, thus establishing perfect synchronism or unison, in which condition the energy of the synchronizing pulse goes entirely to sustain RM.

Thereafter, should contactor 20 contact with Si during the occurrence of a synchronizing signal, the phase'of contactor 20 is advanced to restore unison; should 20 contact with S2, M2 is energized and the phase of 20 is retarded to restore unison. Should the synchronizing pulse not occur within the limits of SI and S2, relay RM will release its armature to arrest movement of contactor 20, and the synchronizing cycle would be repeated.

Referring now to Figs. 6 and 7 which show in detail a preferred form of phase corrector mechanism, drive shaft 6| carries three gears, preferably of the same pitch diameter, mounted thereon side by side. Drive gear GI is securely fastened to drive shaft GI, while intermediate gear G2 and driven gear G3 are loose thereon. Drive gear Gl is provided with a hub 62 on which is rotatably mounted epicyclic train arm 65. Collar 63, which maintains arm 65 in place, encircles hub 62 abutting against a shoulder thereon, and is secured in position by a set screw 64 which extends through hub 62 and bears against drive shaft SI. Gear G3 is provided with a short hub on which is rotatably mounted epicyclic train arm 68. A friction cup 69, containing a friction washer 10 of fibrous material, is mounted upon the hub of G3, being held against rotation relative to G3 by pin TI. The driven part, as for example hub 12 upon which rotary contactor 20 is mounted, is rotatable on drive shaft 6|, being driven by the friction washer I0. A tensioning nut l3, screwed on the threaded end of drive shaft BI, holds the assembly in position on the drive shaft and provides a means for adjusting the frictional force. A set screw locks nut i3 in the position. to which adjusted.

Pinion gear PI is rotatably mounted on arm 65 by any suitable means, such as shoulder rivet 66, so as to mesh properly with GI and the lower part of G2. In like manner pinion gear P2, is rotatably mounted on arm 68 so as to mesh properly with G3 and the upper part of G2, there being a slight clearance space between the two pinions.

Arm 65 is provided with a stop member or finger 35a, while arm 68 is provided with a like member 68a. Corrector magnet MI, of any suitable design, has a plunger positioned to intercept finger 650. when extended and to release same when retracted. Likewise corrector magnet M2 has a plunger adapted to intercept and release finger 68a.

Gears GB and G3 preferably have the same number of teeth, and the same pitch diameter. Gear G2 preferably has the same pitch diameter as gears GI and G3, but is provided with a different number of teeth, say one more or one less tooth. For example, let GI and G3 have I20 teeth while G2 has I2I teeth. Pinion PI and P2 preferably have the same number of teeth, say 30, although this is immaterial.

The operation of the phase corrector mechanism is as follows: Assume that drive shaft BI is in rotation while arms 65 and 68 are held against rotation by MI and M2 respectively.

Then for each revolution of the drive shaft, gear Gl progresses I20 teeth, and since pinion PI meshes with both GI and G2, G2 will likewise progress I20 teeth. Also, since pinion P2 meshes with G2 and G3, G3 will progress I20 teeth; therefore the final driven member will rotate at the same speed as the drive shaft.

Now assume that with the drive shaft still in rotation, magnet MI is energized, releasing arm 65. Then during the revolution following such release, arm 65 is set in rotation with GI and G2, and pinion PI ceases rotation, in effect locking GI and. G2 together, thus preventing any relative motion between them. During this revolution, G2 progresses I2I teeth and since P2 meshes with G2 and G3, G3 likewise progresses I2I teeth. This represents a gain of one tooth pitch for G3, or a phase angle advance of 3 degrees. Hence the driven member advances a like amount in phase with respect to the drive shaft. Assuming that at the end of the revolution, arm 65 is intercepted by MI and stopped, the driven member resumes rotation at the same speed as the drive shaft as before.

Next assume that M2 is energized, releasing arm 68, thus locking G2 and G3 together. At the end of one revolution, G2 lags GI by one tooth pitch of G2 and hence the driven member has been retarded in phase angle with respect to the drive shaft by an amount of approximately 3 degrees.

It is thus seen that by releasing arm 65, the driven member is caused to gain or advance in phase, and by releasingarm 68, the driven member is caused to lose or retard in phase. Ml and M2 are, in effect, triggers which select the direction in which the phase correction is to be applied. Thus the phase of rotary contactor 20 is corrected as maybe necessary to establish and maintain synchronism.

Reference is made to the copending application of Harry J. Nichols, Serial No. 736,383, filed July 21, 1934, in which the phase correcting method and apparatus are more completely described and claimed.

While the methods described herein, and the forms of apparatus for carrying these methods into effect, constitute preferred embodiments of the invention, it is to be understood that the invention is not limited to these precise methods l and forms of apparatus, and that changes may be made in either without departing from the scope of the invention which is defined in the appended claims.

What is claimed is:

1. In a synchronous printing telegraph system, the method of signalling which consists in the steps of sending impulses of uniform polarity indicative of a predetermined phase position of a controlling element, and intermediate said firstmentioned impulses, sending impulses of one or another polarity each indicative of specific printing operations to be performed, receiving said impulses, releasing a rotary controlled element from a predetermined phase position in response to said first-mentioned impulses thereby to establish synchronism, utilizing said second-mentioned impulses to perform specific printing operations in accordance with the characteristics of said impulses, and controlling the phase position of said controlled element responsively to said firstmentioned impulses to maintain synchronism.

2. In a synchronous communication system, the method of signalling which consists in the steps of sending impulses indicative of a predetermined phase position of a controlling element, and intermediate said first-mentioned impulses, sending impulses having predetermined selected characteristics, each indicative of a specific operation to be performed by a receiving machine, utilizing said first-mentioned impulses to synchronize a rotary controlled element with the controlling element, and performing the specific operations desired in accordance with the characteristics of said second-mentioned impulses.

3. In asynchronous single impulse printing telegraph system, the method of signalling which comprises the steps of sending periodic single impulses indicative of a predetermined time interval of a controlling element, and intermediate said first-mentioned impulses, sending aperiodic single impulses of distinctive characteristics each indicative of a specific printing operation to be performed.

4. In a synchronous communication system of the character described the method of signalling which comprises, at the sending station, the steps of sending periodic single impulses for synchronizing purposes, and sending aperiodic impulses of distinctive characteristics each indicative of a specific operation to be performed; and at the receiving station, the steps of receiving said impulses, utilizing said periodic impulses to automatically establish and maintain synchronism, and utilizing said aperiodic impulses of distinctive characteristics to perform the specific operations indicated.

5. In a synchronous single impulse printing telegraph system, the method of signalling which comprises, at the sending station, the steps of sending single impulses of uniform polarity for synchronizing purposes, and sending aperiodic single impulses of one or another selected polarity each indicative of a printing operation to be performed; and at the receiving station the steps of receiving said impulses, utilizing said uniform polarity impulses to synchronize said printing apparatus, and utilizing said selected polarity impulses to perform the printing operations indicated.

6. In a synchronous, remote control system, the method of control which comprises, at the controlling station, the steps of sending timed single impulses for synchronizing purposes, sending characteristic single impulses differentiated as to time or character each indicative of a predetermined selection to be performed; and at the controlled station, the steps of receiving said impulses, utilizing said timed single impulses to synchronize controlled apparatus, and utilizing said timed and characteristic single imupulses to perform the selections indicated.

7. In a synchronous single impulse printing telegraph system, in combination, means for transmitting periodic single synchronizing impulses, means for transmitting single printing impulses distinctive as to time and character each indicative of a printing operation, receiving means for said impulses, a controlled element, means for utilizing said synchronizing impulses to establish and maintain synchronism of said controlled element with said synchronizing impulses, and printing means actuated by said timed and characteristic printing impulses to perform the printing operations indicated by said printing impulses.

8. In a synchronous, remote control system, the method of controlling a plurality of operations of controlled apparatus, which comprises, at the controlling station, the steps of sending periodic impulses of like character for synchronizing purposes, and sending over the same channel aperiodic impulses of unlike character, each indicative of a particular operation to be performed, for selecting purposes; and at the receiving station, the steps of receiving said impulses, utilizing said periodic impulses to establish and maintain synchronism of the controlled apparatus, and utilizing said aperiodic impulses of unlike character to select the particular operations to be performed by the controlled apparatus.

9. In a synchronous remote control system, the method of causing the controlled apparatus to perform any one of N operations as selected by the controlling station, comprising the steps, at the controlling station, of sending periodic impulses for synchronizing purposes, and sending aperiodic impulses for selecting purposes, said aperiodic impulses being differentiated in respect to time into N/2 groups, and as to character into two groups, each impulse being indicative of an operation to be performed; and at the receiving station the steps of receiving said impulses, utilizing said periodic impulses to synchronize the controlled apparatus, and utilizing said aperiodic impulses selectively as to character to cause the controlled apparatus to perform the operations indicated thereby.

10. In a transmission system for synchronous printing telegraphs, in combination, transmission means comprising rotary distributor means including a, rotary contactor and a series of segmentsarranged in successive positions to be engaged by said rotary contactor in timed sequence, means cooperating with said series of segments for transmitting one of a plurality of signal impulses of distinctive characteristics in each of said positions; and means for receiving and utilizing said distinctive signals which comprises receiving instrumentalities selectively responsive to said signals, rotary distributor means including a rotating contactor and a series of receiving segments arranged in positions corresponding to the transmitting segments, synchronizing means for said rotary distributor, and printer actuating means associated in multiple with said receiving segments and actuated selectively in accordance with the character of the receiving signals.

11. In a synchronous printing telegraph apparatus, in combination, rotary distributor means including a rotary contactor and a series of groups of combined transmitting and receiving segments, means cooperating with said distributor means for transmitting periodic synchronizing signals and aperiodic printing signals of predetermined character, receiving instrumentalities selectively responsive to received signals of the character described signals, synchronizing means including a second rotary contactor responsive to received periodic synchronizing signals, printer actuating means, and operating means connected with segments of said series and energized selectively in accordance with the character of received printing signals.

12. In a printing telegraph system, the combination for combining signalling channels and signalling apparatus which comprises a combined sending and receiving distributor including a rotary contactor and two series of combined sending and receiving segments, two groups of combined printer actuating and transmitting members transmitting and receiving through individual segments of said series, means including said rotary contactor and segments for producing printing signals of distinctive character, receiving means selectively responsive to received printing signals of similar distinctive character, two groups of operating members for said printer actuating members simultaneously connected in multiple with a pair of said segments and selectively energized therethrough by said receiving means, and switching means for changing said apparatus from transmitting to receiving condition and vice versa.

13. In printing telegraph transmitting apparatus, means for transmitting signals difierentiated as to time or character comprising in combination, a plurality of combined printer actuating and transmitting members operatively arranged in two groups, means to predetermine the character of signals transmitted by said groups, an energy source, and rotary distributor means including a series of paired sending segments and associated respectively with said actuating and transmitting members, and a rotary contactor contacting simultaneously pairs of said segments.

14. In printing telegraph receiving apparatus, in combination. a plurality of printer actuating members, rotary distributor means including a rotary contactor and a series of paired receiving segments, a plurality of.electromagnetic operat ing means for said printer actuating members segments, and receiving means selectively responsive to the character of received signals and adapted to cause operation of one member of a pair of operating means in accordance with the character of the received signal.

15. In printing telegraph receiving apparatus. in combination, a plurality of printer actuating members; rotary distributor means including a rotary contactor and a series of paired receiving segments; electromagnetic operating means for said printer actuating members operatively arranged in pairs, and electronic receiving means selectively responsive to the character of received signals and adapted to energize one member of a pair of operating means in accordance with the character of the received signal.

16. In printing telegraph receiving apparatus, the combination of means claimed in claim 15, and current interrupting means forsaid electronic receiving means.

17. In printing telegraph apparatus, in combination, combined sending and receiving apparatus comprising rotary distributor means including a rotary contactor and two series of combined sending and receiving segments arranged in pairs, a plurality of combined printer actuating and transmitting members operatively arranged in groups, means to predetermine the character of signals transmitted by each of said groups, an energy source supplying operating energy, a plurality of operating means for said printer acutating members associated in pairs with said series of segments, and receiving means selectively responsive to the character of received signals and adapted to energize one of each. group of operating means in accordance therewith.

18. In printing telegraph apparatus, the combination in accordance with claim 17, means for producing synchronizing signals, and means for receiving and utilizing said synchronizing signals to establish and maintain the rotary distributor at the receiving station in synchronism with that at the sending station.

19. In printing telegraph apparatus, incombination, combined sending and receiving apparatus comprising rotary distributor means, a plurality of combined printer actuating and transmitting members operatively arranged in two groups, means operable to predetermine the character of signals transmitted by each of said groups, a source of electrical current, a plurality of operating means for said printer actuating members operatively arranged in groups of two,

receiving means selectively responsive to the character of received signals and adapted to select one of said groups to be energized, and energizing current interrupting means exterior to said rotary distributor means, and switching means for changing said apparatus from transmitting to receiving condition and vice versa.

20. In printing telegraph apparatus, in combination, combined sending and receiving apparatus comprising rotary distributor means including a rotary contactor and a series of comeach adapted to operate one of said printer actuating means and arranged in corresponding series; relay means selectively responsive to the polarity of received signals and acting to connect in' circuit one of said series of operating means in accordance with the polarity of the received signal; current interrupting means connected in circuit with said relay means to disconnect said circuit after a predetermined time interval, and switching means to change said apparatus from transmitting to receiving condition and vice versa.

21. In a synchronous printing telegraph system; the method of establishing communication with a receiving station which consists in the steps of sending periodic single impulses for call signalling and synchronizing purposes, utilizing said periodic impulses at the receiving station to produce a call signal, and thereafter utilizing said periodic signals to synchronize the receiving apparatus of the receiving station thereby to establish telegraphic communication.

22. In a synchronous printing telegraph system, in combination, controlling means for producing periodic synchronizing signals, call signal means responsive to said periodic signals, synchronizing means responsive to said periodic signals, and switching means whereby either the call signal means orthe synchronizing means is made responsive to the synchronizing signals.

23. In a rotary distributor for remote controlled apparatus, in combination, a rotary contactor, a common ring, and a series of signalling segments comprising a synchronizing segment, one or more corrector segments associated therewith, and two series of signalling segments operatively arranged in pairs.

24. In a rotary distributor for remote controlled apparatus, in combination, a rotary contactor, a common ring, a series of segments including a synchronizing segment, one or more corrector segments associated therewith, and two series of signalling segments operatively arranged in pairs, and phase correcting means for said rotary contactor operatively associated with said corrector segments.

25. In a communication system of the character described, means adapted to be selectively utilized for transmitting and receiving purposes including a printing mechanism having a pinrality of actuable elements, circuits corresponding respectively to the several operations to be performed by the elements of said mechanism and arranged in groups of a plurality of circuits each, distributor means arranged to connect with the circuits of a group simultaneously and with all the groups sequentially, means including said circuits and distributor means for generating distinctive signals characteristic of a predetermined element when the apparatus is in transmitting position, and for selecting and actuating the predetermined desired elements in accordance with the characteristics of received signals when the apparatus is in receiving position, and switching means for changing the position of said device from transmitting to receiving condition and vice versa.

HARRY J. NICHOLS.

HENRY L. THOLSTRUP. 

